[05.39] Pulmonary Diagnostics_ ABG V2.1.pdf

Measure gas exchange or ventilation status, and check for acid-base balance disorders

What are the two main uses of Arterial Blood Gas (ABG)?

COPD, Respiratory failure, Respiratory infections (e.g., pneumonia)

What are three respiratory diseases assessed using ABG?

Monitoring during invasive or non-invasive ventilation

What specific clinical status is monitored using ABG?

Diabetic ketoacidosis (DKA), Kidney disease, Sepsis, Shock

What are four diseases where ABG checks for acid-base balance disorders?

Radial artery

What is the most commonly used artery for performing ABG?

Superficial and easily palpable over the radial styloid process

What two characteristics make the radial artery commonly used?

Brachial artery and Femoral artery

What are two other arteries used in performing ABG?

Hydrogen ions (H+)

What is the pH based on in arterial blood?

Measurement of acidity or alkalinity (acid-base balance)

What does the pH measure?

7.35–7.45

What is the normal range for pH?

Acidosis

What condition is indicated if pH < 7.35?

Alkalosis

What condition is indicated if pH > 7.45?

Normal, maximally compensated, or mixed

What three conditions may be indicated if pH is 7.35–7.45?

7.4

What is the clinical cut-off for pH?

Alkalosis

What condition is indicated if pH > 7.4?

Acidosis

What condition is indicated if pH < 7.4?

Partial pressure of carbon dioxide in arterial blood

What does PaCO2 stand for?

Respiratory component of ABG

What component of ABG is PaCO2?

Measures ventilation

What specific physiological process does PaCO2 measure?

35–45 mmHg

What is the normal range for PaCO2?

More acidic

What does more PaCO2 in the arterial blood indicate?

More alkalotic

What does less PaCO2 in the arterial blood indicate?

Bicarbonate

What is HCO3?

Calculated concentration in arterial blood

How is HCO3 measured/determined?

Chemical buffer produced by the kidneys to neutralize acid

What is the function of Bicarbonate?

Metabolic component of ABG

What component of ABG is HCO3?

22–26 mEq/L

What is the normal range for HCO3?

Measured partial pressure of oxygen in arterial blood

What does PaO2 stand for?

80–100 mmHg

What is the normal range for PaO2?

94–100%

What is the normal range for O2 sat?

Check the pH: is there acidosis or alkalosis?

What is Step 1 in ABG reading?

Is the disturbance respiratory or metabolic?

What is Step 2 in ABG reading?

Is there appropriate compensation for the primary disturbance?

What is Step 3 in ABG reading?

For metabolic acidosis: Calculate the anion gap

What is Step 4 in ABG reading?

If with increased anion gap: Assess the relationship between the increase in anion gap and decrease in HCO3

What is Step 5 in ABG reading?

Is there adequate oxygenation?

What is Step 6 in ABG reading?

Primary disorder

What type of disorder is determined in Step 1?

Same-Metabolic, Opposite-Respiratory

What mnemonic is used for determining the type of disturbance in Step 2?

Metabolic Acidosis

What primary disturbance results from a decrease in pH and a decrease in PaCO2 (↓↓)?

Respiratory Acidosis

What primary disturbance results from a decrease in pH and an increase in PaCO2 (opposite)?

Metabolic Alkalosis

What primary disturbance results from an increase in pH and an increase in PaCO2 (↑↑)?

Respiratory Alkalosis

What primary disturbance results from an increase in pH and a decrease in PaCO2 (opposite)?

↓ HCO3

What is the main disturbance in Metabolic Acidosis?

↓ PaCO2

What is the expected compensation for Metabolic Acidosis?

Increase in minute ventilation (hyperventilation) or increase in the respiratory rate

What physiological mechanism causes the expected compensation for Metabolic Acidosis?

↑ PaCO2

What is the main disturbance in Respiratory Acidosis?

↑ HCO3

What is the expected compensation for Respiratory Acidosis?

Increase in reabsorption of HCO3 in the proximal convoluted tubules of the kidneys, increase in H+ excretion in the distal convoluted tubule

What renal mechanisms cause the expected compensation for Respiratory Acidosis?

Airway obstruction (upper or lower), CNS depression, Sleep disordered breathing, Neuromuscular impairment, Ventilatory restriction, Increased CO2 production, Incorrect mechanical ventilation settings

What are six causes of Respiratory Acidosis?

Shivering, rigors, seizures, malignant hyperthermia, hypermetabolism, increased intake of carbohydrates

What five conditions are examples of increased CO2 production causing Respiratory Acidosis?

↑ HCO3

What is the main disturbance in Metabolic Alkalosis?

↑ PaCO2

What is the expected compensation for Metabolic Alkalosis?

Decrease in minute ventilation (hypoventilation) or decrease in the respiratory rate

What physiological mechanism causes the expected compensation for Metabolic Alkalosis?

Hypovolemia with Cl- depletion (GI loss of H+ or Renal loss H+), Hypervolemia with Cl- expansion (Renal loss of H+)

What are the two major categories of causes of Metabolic Alkalosis?

Vomiting, gastric suction, villous adenoma, diarrhea with chloride-rich fluid

What four GI losses of H+ can cause Metabolic Alkalosis?

Loop and thiazide diuretics, post hypercapnia

What two causes of renal loss of H+ can cause Metabolic Alkalosis?

Heart failure, Cirrhosis, Nephrotic syndrome

What three edematous states cause renal loss of H+ in Hypervolemia with Cl- expansion?

Hyperaldosteronism, Hypercortisolism, Excess ACTH, Exogenous steroids, Hyperreninemia, Severe hypokalemia, Renal artery stenosis, Bicarbonate administration

What eight causes of renal loss of H+ are listed in hypervolemia/Cl- expansion?

↓ PaCO2

What is the main disturbance in Respiratory Alkalosis?

↓ HCO3

What is the expected compensation for Respiratory Alkalosis?

Decrease in reabsorption of HCO3 and decrease in H+ excretion by kidneys

What renal mechanisms cause the expected compensation for Respiratory Alkalosis?

CNS Stimulation (fever, pain, fear, anxiety, CVA, cerebral edema, brain trauma, brain tumor, CNS infection), Hypoxemia or hypoxia, Stimulation of Chest Receptors, Drugs/hormones, Incorrect mechanical ventilation settings

What are five categories of causes of Respiratory Alkalosis?

Pulmonary edema, pleural effusion, pneumonia, pneumothorax, pulmonary embolism

What five conditions are examples of Stimulation of Chest Receptors causing Respiratory Alkalosis?

Salicylates, catecholamines, medroxyprogesterone, progestins

What four drugs/hormones can cause Respiratory Alkalosis?

Uncompensated

What status means there is no change in expected compensation, and the pH is not within the normal range?

Partial or submaximal compensation

What status means expected compensation values change outside normal limits, but the pH is not within normal range?

Maximal compensation

What status means expected compensation values change outside normal limits, and the pH is within normal range?

Concomitant respiratory alkalosis

What condition is indicated if PaCO2 is less than the computed range in Metabolic Acidosis?

Winter’s Formula: PaCO2 = (1.5 × HCO3) + 8 ± 2

What formula is used to check for appropriate compensation in Metabolic Acidosis?

Concomitant metabolic alkalosis

What condition is indicated if HCO3 is greater than the computed range in Respiratory Acidosis?

HCO
3
​
=24+

(PaCO
2
​
−40)/10

±3

What is the formula for the expected compensation in Respiratory Acidosis?

Concomitant respiratory acidosis

What condition is indicated if PaCO2 is greater than the computed range in Metabolic Alkalosis?

PaCO
2
​
=40+0.6(HCO
3
​
−24)

What is the formula for the expected compensation in Metabolic Alkalosis?

Concomitant metabolic acidosis

What condition is indicated if HCO3 is less than the computed range in Respiratory Alkalosis?

HCO
3
​
=24−{2

(40−PaCO
2
​
)/10

}

What is the formula for the expected compensation in Respiratory Alkalosis?

Metabolic Acidosis

For which primary disorder must the Anion Gap be calculated?

~12 mEq/L

What is the normal anion gap?

AG=(Na−Cl+HCO
3
​
)−12±2

What is the Anion Gap Formula used in the exercises?

Methanol intoxication, Uremia, Diabetic ketoacidosis/alcoholic ketoacidosis/starvation ketoacidosis, Paraldehyde toxicity, Isoniazid, Lactic acidosis, Ethanol/ethylene glycol intoxication, Salicylate intoxication

What are eight causes of High Anion Gap Metabolic Acidosis (HAGMA)?

Diabetic ketoacidosis

What is one of the most common causes of HAGMA?

Tissue ischemia or altered cellular metabolism

What are two causes of Lactic acidosis?

GI loss of HCO3, Renal loss of HCO3, Renal tubular disease

What are three major categories of causes of Non-Anion Gap Metabolic Acidosis (NAGMA)?

Diarrhea, ileostomy, proximal colostomy, ureteral diversion

What four GI losses of HCO3 can cause NAGMA?

Proximal renal tubular acidosis (RTA), Use of carbonic anhydrase inhibitor (acetazolamide)

What two renal losses of HCO3 can cause NAGMA?

Acute tubular necrosis (ATN), Chronic renal disease, Distal RTA, Aldosterone inhibitors or absence, NaCl infusion, total parenteral nutrition (TPN), NH4+ administration

What seven conditions are examples of renal tubular disease causing NAGMA?

Assess the relationship between the increase in anion gap and decrease in HCO3

What is Step 5 of ABG reading (if increased anion gap)?

ΔAG/ΔHCO
3
​

What ratio is calculated to assess the relationship between the change in anion gap and the change in HCO3?

1.0–2.0

What range of the ΔAG/ΔHCO
3
​
ratio indicates uncomplicated anion gap metabolic acidosis (Pure HAGMA)?

< 1

What ratio indicates concurrent Non-Anion Gap Metabolic Acidosis (NAGMA)?

2

What ratio indicates concurrent Metabolic Alkalosis?

Compute for the desired PaO2 for age

What must be calculated in Step 6 to assess adequate oxygenation?

DesiredPaO
2
​
for age =104−(age×0.43)

What is the formula for the desired PaO2 for age?

7.35–7.45

What is the range of normal value for pH level?

Bicarbonate

What is a chemical buffer produced by the kidneys to neutralize acid?

Uncompensated

What was the compensation status of the 54/F with pH 7.25 and PaCO2 60 (Exercise 1)?

Inadequate oxygenation

What was the oxygenation status of the 54/F patient in Exercise 1 (Actual PaO2 65 vs. Expected 80.78)?

Respiratory acidosis, uncompensated with inadequate oxygenation

What was the full ABG report for the 54/F patient in Exercise 1?

Maximal compensation

What was the compensation status of the 36/F patient with metabolic alkalosis (Exercise 2) whose pH was 7.423?